1. Field of the Invention
The present invention concerns a method for applying an elastomer on a sheath.
It also concerns a pad printing machine adapted to use that method.
The invention further concerns a protective sheath and more particularly a textile sheath (i.e. a sheath consisting of interlaced filaments) coated with an elastomer layer obtained by this method and cut to length.
In particular, the present invention finds its application in textile sheaths used for the protection of exhaust gas recycling (EGR) tubes in motor vehicles.
These textile, generally knitted, sheaths are obtained by cold cutting into longitudinal sections of predetermined length a textile sheath of great length, possibly measuring up to several meters.
2. Description of the Related Art
When a textile sheath is cut to length, the ends of the sheath splay and this splaying is accentuated by handling.
Thus the sheath is deformed at the ends and loses its protective characteristics when it is installed around a tube or a pipe.
In a correlated way, cutting the sheath causes pollution because pieces of the filaments are detached from the sheath.
In particular stitches are cut when a knitted sheath is cut to length. Pieces of the filaments of these stitches are detached from the sheath, causing pollution.
One solution for preventing pollution by cutting the sheath to length consists in passing the sheath over vibrating tables to eliminate the pieces of the stitches detached from the sheath.
This solution cannot achieve satisfactory pollution prevention if pieces of the stitches detached from the sheath remain stuck to the sheath and become detached only when the sheath is transported or when the sheath has been installed.
Furthermore, this solution prevents neither deformation of the sheath nor splaying of the ends.
The document U.S. Pat. No. 5,186,992 describes a method for avoiding splaying of the ends of the sheath after cutting.
The method consists in applying an elastomer by passing the sheath into a bath of liquid elastomer. The sheath covered with elastomer is then dried in a hot air oven at a temperature of around 150° C.
However, the elastomer layer obtained by this method is not uniform and is thicker than necessary. This implies an excessive consumption of elastomer as well as imprecise application of the elastomer.
Furthermore, heating the sheath can lead to deformation of the sheath by modification of the dimensions and elasticity of the sheath.